I am so guilty of obsessing over my kcal burn at the gym compared to my calory intake, especially since I got my new Fitbit Charge HR. It’s funny how we perceive something to be so true and solid, while at the same time, it’s really fooling us. For example, how do you know your food contains exactly the amount of calories you’ve calculated? You actually don’t, its all an estimation, which is fine by me, but thought you might want to know before you stress out over a few of them 😉
So now something about the fat burn zone. It has been a myth for a long time, that in order to lose weight or lose fat, you need to do low intensity steady state (LISS) workouts to burn fat. The myth says your heartrate needs to be in a certain zone to maximise the amount of fat burned. There is a bit of truth behind it, but not in a way you might think. I’ll try to explain.
Your body contains a certain amount of glycogen, which is basically long chains of glucose. There’s some storage in the muscles and in the liver. It’s a fast and easy way of providing the body energy fast when it needs it. Like in emergency situations, where you have to run away fast in case of danger for example. The thing is, your body really wants to preserve this storage for these emergencies, but will use is when it’s necessary. Fat burning is slower though, it needs more processes to get to energy so it’s not efficient in emergencies. So, for example, you go for a long and sturdy walk (LISS), the body will burn some glycogen, but finds out you go slow and steady (no emergency), so it starts up the processes of burning fat. Slowly, the amount of fats used as energy will increase and the amount of glycogen used will decrease. It will never go to 0%, but because of the slow and steady pace, you’ll have a higher % of fatburn in comparison to the fast and shorter situations where you’ll get a higher % of glycogen burn.
So up to now, you’ll be like, ok, you said it’s a myth but this really sounds like LISS is the way to go for fat burn? I’ll try to get to the clue. It is ALL about energy in and energy out. If you burn more energy than you eat, you’ll lose weight and vice versa. It doesn’t really matter if you burn a higher fat %, because in the end, the body will restore the glycogen stores, using the fat stores if you don’t eat more than you burn! And guess what, the more intense the workout, the more kcal you burn, so in the end, you’ll also burn more fat with intense workouts. There’s been a lot of research about High Intensity Interval Training (HIIT), which is short bursts of high intensity training followed by short periods of lower intensity training. It happens to be that you’ll burn a lot more kcal during these workouts, but also AFTER them, making them very efficient for losing weight!
So before I conclude I’ll have to add something else. There actually are other benefits of LISS, like getting more endurance. You’ll not hear me say that you shouldn’t do LISS. It’s just that I think it’s good to know what type of exercise benefits are out there and what will fit your goal! Personally, I’ve been heavy weightlifting (which is also a bit of a HIIT workout) since the start of my journey. For the first 10 months or so, I never did any cardio. Right now, I do 20 minutes of HIIT intervals on the elliptical after weightlifting. I also try to get 10.000 steps daily, which means I go for walks almost every day, which is my LISS workout. It keeps me active and energetic!